JPH05167066A - New quantum-well switching element having exciting and emitting capability - Google Patents

Abstract

PURPOSE: To provide a diode switching element of semiconductor-insulator- semiconductor structure having a possibility of higher rate optoelectronic switching and exhibiting a good laser performance, a prominent negative differential resistance and a high sensitivity. CONSTITUTION: A buffer layer 14 is formed on a GaAs substrate 12, and an n-type clad layer 16 is formed on the buffer layer 14 and an undoped i-region is provided thereon. The i-region includes first and second quantum well layers 20, 24 isolated by a quantum well barrier layer 22 provided between two waveguide layers 18, 26 and it must include at least one quantum well. A lightly doped p-type clad layer 28 is provided on the top of the i-region and a connection layer 30 is provided thereon. Furthermore, first and second connection terminals 36, 38 are provided thus obtaining a two terminal element. A diode thus obtained has good laser emission properties, a prominent negative differentiation resistance and a high optical sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor-insulator-semiconductor (SIS) structure diode, and more particularly to a novel quantum well optoelectroswitching device having a pumping emission capability.

[0002]

Microwave semiconductor devices are commonly used in the generation, amplification, detection and control of high frequency electromagnetic energy. However, at relatively high frequencies, the usefulness of conventional semiconductor devices is severely limited by the high frequency effects. Gallium arsenide other than silicon (G
The use of III-V compounds such as aAs) or indium phosphide gives a significant improvement. This is because the electron mobility of these materials is several times higher than that of silicon, resulting in lower series resistance.

Various optoelectroswitching devices have been developed that exhibit stimulated emission. Such elements are
It is attractive for potential applications in microwave generation, high speed logic switches, integrated circuit-like optical interconnects, optical computing systems and optoelectronic integrated circuits (OEICs). The double barrier resonant tunneling diode is integrated as a single crystal with a quantum well (QW) laser to form an optical bistable element. Double heterojunction structure optoelectroswitching (DOES) devices and surface vertical propagation electrophotonic (VSTEP) devices in combination with single quantum well lasers have been demonstrated as lasers to achieve pumped emission. However, the existence of pn junctions has been found to limit the efficiency and power of these devices. Moreover, many opto-electro switching device structures are not compatible with OEICs and therefore cannot be easily incorporated into OEICs.

Therefore, it is desirable to have an optoelectroswitching device that has the potential for faster optoelectroswitching. Furthermore, it is desirable to have devices that exhibit good laser performance, significant negative differential resistance and strong sensitivity. Furthermore, it is desirable to have devices that are compatible with OEIC technology.

[0005]

SUMMARY OF THE INVENTION In accordance with the teachings of the present invention, a SIS structure diode is provided. The diode has a substrate with a buffer layer on top. The n-type cladding layer is placed on top of the buffer layer. The undoped i-region is located on top of the buffer layer. The i-region includes at least one quantum well located between two waveguiding layers.
The lightly doped p-type cladding layer is placed on top of the i region. The connection layer is further placed on top of the o-type cladding element.

[0006]

EXAMPLE Returning to FIG. Gallium arsenide (GaAs) / gallium aluminum arsenide (Ga) having a plurality of fabrication layers
An AlAs) semiconductor-insulator-semiconductor SIS structure diode 10 is shown. GaAs / GaAlAs SI
The S-structure diode 10 is essentially an opto-electro switching device that exhibits s-type negative differential resistance at room temperature and performs high-performance stimulated emission. This element may be a two-terminal element 10 or may be a three-terminal element. The element is optically and / or electrically switched to produce an optical or electrical output. This device structure resembles a conventional separate confinement heterojunction quantum well laser, and thus can be easily integrated with an optoelectronic integrated circuit.

The GaAs / GaAlAs SIS structure diode 10 includes a substrate 12. Substrate 12 comprises heavily doped n ⁺ GaAs. The n ⁺ type GaAs buffer layer 14 is provided on the top of the substrate 12. The buffer layer 14 is about 1.0 micrometer thick and has a size of 6 × 10 ¹⁸ cm.
^-3 with Se doping. This buffer layer 14 essentially smoothes the substrate 12. The GaAlAs cladding layer 16 is provided on top of the buffer layer 14.
The n-type cladding layer 16 is formed of Ga _0.6 Al _0.4 As and is doped with Se at a concentration of 4 × 10 ¹⁸ cm ^-3.
It is 1.2 micrometers thick.

The undoped i region is located on top of the cladding layer 16. i region is undoped Ga _0.8 Al
_It includes a first waveguiding layer 18 of _0.2 As. The first waveguiding layer 18 provides a guide for stimulated emission and is about 700 Å thick. A first undoped GaAs quantum well 20 is placed on top of the first waveguiding layer 18. The first quantum well 20 is about 700 Å thick. The GaAlAs quantum well barrier layer 22 is the quantum well 2
It is installed on the top of 0. The quantum well barrier layer 22 is about 9
It is 0 angstrom thick. The second GaAs quantum well 24 is provided on top of the quantum well barrier layer 22. The second well 24 is about 70 angstroms thick. A second waveguiding layer 26 of undoped Ga _0.8 Al _0.2 As is further placed on top of the second quantum well 24.
The second waveguiding layer 26 is approximately 700 Å thick and also provides a guide for stimulated emission.

The i region shown in FIG. 1 includes first and second quantum well layers 20 and 24 separated by a quantum well barrier layer 22. For the purposes of this invention, the i-region need only include at least one quantum well layer. If only one quantum well is provided, no quantum well barrier layer is needed. However, 2
When the above quantum well layers are included, the quantum well layers need to be separated by the quantum well barrier layer.

At the top of the i region, Ga _0.6 Al _0.4 A
It is a p ⁻ -type GaAlAs cladding layer 28 made of s.
The p ^- type cladding layer 28 is lightly doped with Zn doping at a concentration of 5 × 10 ¹⁵ -10 ¹⁶ cm ^-3 . The p ^- type cladding layer 28 is about 1.2 micrometers thick.
The p ⁻ -type cladding layer 28 confines the stimulated emission and constitutes a barrier to the holes, preventing the holes from recombining under low bias conditions.

A p ⁺ type GaAs connection layer 30 is provided on top of the p ⁻ type cladding layer 28. The p-type connection layer 30 is about 0.5 micron thick and is heavily doped with Zn to ensure a good tunnel ohmic contact with the ohmic connection. The p-type ohmic connection layer 32 includes the p-type connection terminal 3
It is placed on top of the connection layer 30 having 6 to allow connection with external elements. The p-type ohmic connection layer 32 contains a conductive material such as Ti-Pt-Au. Separately from this, the p ⁺ type connection layer 30 and the P type ohmic connection layer 32
Can be replaced by n ⁺ type connection and ohmic connection layers. Similarly, the n-type ohmic connection layer 34 having the n-type connection terminal 38 is provided to provide a connection to an external connection.
It is installed at the bottom of the structural diode 10. The n-type ohmic connection layer 34 includes a conductive material such as Ni-AuGe-Ni-Au.

[0012] In general, the diode structure 10 obtained as a result, the four layers n ⁺ -i-p similar the OEIC and conventional separation isolation heterojunction quantum well structure can be integrated ^- a structure in .. The n ⁺ -i-p ^- structure, metal - behave in the same manner as the semiconductor (MIS) form the capacitor, the semiconductor - - insulator insulator - semiconductor (S
I) Form condenser. p ⁻ −p ⁺ structure is GaA
s / GaAlAs heterojunction. Therefore, this diode structure element has SIS and p ^-- p ⁺ GaAs / G
It includes two junctions that are aAlAs heterojunction capacitors. The diode structure element 10 can be manufactured by known conventional techniques such as wet chemical etching, reactive ion etching, ion beam etching and other dry etching techniques.

FIG. 2 illustrates GaAs according to another embodiment of the present invention.
A / GaAlAs SIS structure diode 10 'is illustrated. The structure diode 10 'is the diode structure 1
It is manufactured or constructed in the same manner as the diode structure 10 shown in FIG. 1, except that 0'includes an undoped semi-insulating GaAs substrate 12 '. The semi-insulating GaAs substrate 12 'reduces parasitic capacitance and provides faster operation and thus higher performance. Furthermore, the n-type ohmic connection layer 34 is
It is placed on top of buffer layer 14 and is separated from the other layers of device 10 '.

FIG. 3 illustrates a three terminal device 40 according to another embodiment of the present invention. This three terminal device 40 is the device 10 'shown in FIG. 2 except that a third terminal is added to form a three terminal device known as a transistor.
It is constructed by the same method as. Another third terminal 42 is i
It contains Si ions implanted in the layers of the region. The third terminal 42 forms a transistor-like gate and is connected to the ion implantation part via the ohmic layer 44. The p-type connection layer terminal 36 forms the emitter terminal of the three-terminal element 40. The n-type connection terminal 38 forms the n-type connection collector of the three-terminal element 40.

1 to 3 show an optoelectroswitching element that provides stimulated emission. The element can be configured as a terminal element 10 configured as two diodes. In addition to the third terminal, the element can be configured as a three terminal element to form a transistor. The switching mechanism of the device is shown in FIGS.
This is shown by the energy band diagram shown in c. Figure 4a illustrates an energy band diagram in thermal equilibrium. The conductivity of the undoped i region is reverse biased to p ⁺
If greater than that of the GaAs / p ⁻ GaAlAs (p ⁺ / p ⁻ ) connection 52, much of the applied voltage will drop across the p ⁺ / p ⁻ connection 52. The current-to-voltage (IV) characteristic of the device under reverse bias thus behaves similarly to a reverse biased pn junction.

FIG. 4b illustrates the result of applying a forward bias. When the forward bias increases, the free electrons become p ⁺ / p
^- p through the junction 52 ^- swept out from the region, the depletion layer 5
8 grows. Electron hole pairs are generated in the depletion layer 58. This is because the electrons are swept out through the p ⁺ / p ⁻ junction 52 and the holes are p ⁻ GaAlAs / undoped GaAlA.
Swept to the s (p ⁻ / i) interface. As a result, the generated holes accumulate at the (p ⁻ / i) interface 54. Under these conditions, holes cannot be injected into the undoped i-region through the wide band gap barrier. Further, the electrons are limited by tunneling through the barrier resulting in significant voltage drop and large series resistance across the depletion region 58 and the undoped i region. As a result, these regions therefore absorb much of the potential, providing a high potential, low current, different current flow than in the off state.

When the forward bias increases, the hole current flowing through the p ⁺ / p ⁻ junction 52 increases with the aggregation of holes at the (p ⁻ / i) interface 54. The aggregation of holes is the depletion region 5
Promote heat and / or light generation of electron hole pairs within 8. This agglomeration also causes punch-through of the p ⁺ / p ⁻ junction 52, p
^It may also be caused by the avalanche of the layer and / or the initial electron tunneling current from the n ⁺ / i junction 56. Hole agglomeration and increased hole current result in increased electron current through the n-type GaAlAs / undoped GaAlAs (n ⁺ / i) junction 56. This increased electron current is p ⁺ / p ^-
Field back to the junction 52, increasing the electron and hole currents that flow through the p ⁺ / p ⁻ junction 52. p ⁺ / p
^- hole current flowing through the junction 52, the depletion region 58
The internal current loop gain is
Exceeds 1. The feedback of the current loop will therefore be positive, increasing regenerative switching. As a result of this regeneration process, the device displays an s-type negative differential resistance (NDR) such that the voltage decreases and the current increases. In this state, the p ⁺ / p ^- junction 52 and the n ⁺ / i junction 56 are formed as shown in FIG.
It is strongly forward biased as shown in C.

Immediately after the voltage drops, rapidly increased electron and hole currents are injected into the quantum well 50 in the i-region, where they recombine and provide instantaneous and / or stimulated emission. This recombination reduces the internal current gain below 1 and the device reaches a stable state. For an electric field greater than 10 ⁴ V / m, the hole gas is heated and a thermoelectron stable emission is generated across the barrier. However, since the quantum well has a minimum potential in the i region, hot holes are injected into the quantum well instead of being swept from the high field region and then recombined in the n-type GaAlAs cladding layer. This injection mechanism prevents impact ionization due to high electric fields. Furthermore, the recombination of electrons and holes in the quantum well is
Excited emission is generated by the inherent wave guide provided by the cladding layer.

FIG. 5 shows the current vs. voltage (I-
V) shows the characteristics. Since QW has the lowest potential in the i region, hot holes are injected into the QW without being swept from the high field region and recombine in n-GaAlAs. Since the electrons and holes recombine in the QW, the stimulated emission occurs with the inherent wave guide provided by the cladding element.

FIG. 6 illustrates the device output power versus current. A threshold of 600 milliamps, a differential quantum efficiency of 67 percent and a power in excess of 50 milliwatts per facet can be obtained under quasi continuous wave conditions. This gives opto-electro switching devices exhibiting stimulated emission the best performance in terms of power, differential quantum efficiency and threshold. The device power measured against Figure 3 was less than 50 milliwatts per facet.
However, when the device is fully optimized, the device
More improved threshold current density, differential quantum efficiency and output power can be provided.

The switching elements described herein result in two or three terminal elements. The device provides fast opto-electro switching and produces stimulated emission. From the above,
The present invention allows a user to obtain an off-electroswitch element having a diode structure with stimulated emission. Accordingly, the present invention has been described in connection with specific embodiments, but is not intended to be limited except as defined by the claims. Those skilled in the art will understand that other improvements can be made by studying the specification and drawings without departing from the spirit of the invention.

[Brief description of drawings]

FIG. 1 GaAs / GaAlAs SIS according to the present invention.
Schematic cross section of a structural diode,

FIG. 2 is GaAs / GaAl according to another embodiment of the present invention.
Schematic sectional view of an As SIS structure diode,

FIG. 3 is a three-terminal GaAs / G according to another embodiment of the present invention.
a sectional view of an aAlAs SIS structural element,

FIG. 4 GaAs / GaAlAs SIS according to the invention.
An energy band diagram illustrating the energy change of the structural element,

FIG. 5: GaAs / GaAlAs SIS according to the invention.
Diagram showing the current-voltage characteristics of the structural element,

FIG. 6 GaAs / GaAlAs SIS according to the present invention.
5 is a graph showing output power vs. current of a structural element.

[Explanation of symbols]

 10 GaAs / GaAlAs SIS structure diode 12 substrate 14 buffer layer 16 cladding layer 18 first waveguide layer 20 first quantum well 22 quantum well barrier layer 24 second quantum well 26 second waveguide layer 28 cladding layer 30 Contact layer 32,34 Ohmic contact layer 36 Connection terminal

Claims (8)

[Claims] 1. A structural diode device for providing optoelectroswitching, the device comprising: a substrate, a buffer layer disposed on the substrate, an n-type cladding layer disposed on top of the buffer layer, Further comprising an undoped i-type region having at least one quantum well located on top of the n-type cladding layer, the i-type region further being located below the quantum well. A second waveguiding layer and a second layer on top of the quantum well
A p-type clad layer disposed on top of the i-type region and the i-type region, the p-type clad layer being lightly doped to form a barrier to holes. A structural diode device having a layer and a connection layer provided on top of the p-type cladding layer. 2. The i-region further comprises a first waveguiding layer located below the quantum well, and a second waveguiding layer located on top of the quantum well. element. 3. The device according to claim 2, further comprising a first ohmic connection layer disposed on top of the GaAs connection layer. 4. A first connecting to the one ohmic connection layer
4. The device according to claim 3, further comprising: a connection terminal of 1), and a second connection terminal connected to the second ohmic connection layer. 5. The device according to claim 2, wherein the i region includes a plurality of quantum wells and a barrier layer located between the quantum wells. 6. The device according to claim 4, wherein the connection layer contains p ⁺ -type GaAs. 7. The device according to claim 4, wherein the connection layer includes n ⁺ -type GaAs. 8. An optoelectronic switching device having an input means for receiving an optical or electrical bias signal, the device forming a barrier when the bias input signal is below a predetermined voltage, and the bias signal is An optoelectroswitching device comprising means for providing a depletion layer that provides stimulated emission above a predetermined voltage.